In order to meet the demand for increasing areal densities in magnetic tape, many technological innovations are required. A first technological innovation is the ability to write multiple data tracks on a magnetic tape simultaneously. This can be accomplished through the use of a multi-element tape head containing a sequence of write elements, each write element writing one track across the width of the tape. In order to improve data reliability, a read element corresponding to each write element reads the magnetic field from the tape immediately after it is written. This technique is known as read-while-write. To increase data transfer, the tape may be written as it travels in either direction across the tape head. This requires a read element on either side of each write element, resulting in a read-write-read head configuration.
A second technological innovation increasing magnetic tape areal density is the continued shrinking of data track width and spacing between data tracks. This reduction in track geometry requires a corresponding reduction in the size and spacing of read and write elements. Thin film technologies have permitted the dimensions of tape head elements to shrink at a rate mirroring that of the integrated circuit industry.
Increasing track densities and decreasing tape head geometries create many new design challenges and magnify existing problems. One such difficulty is feedthrough. Feedthrough occurs during a read-while-write operation when a read element receives a magnetic signal directly from a write element transmitted either through the air or through the tape head itself. This direct magnetic signal appears as noise degrading the signal read from the magnetic tape.
Many techniques to reduce feedthrough have been developed. Most of these techniques require the addition of magnetically permeable shields around read elements, write elements, or both. The addition of such magnetic shields requires additional material, additional processing steps, and increased head size. What is needed is a technique for reducing feedthrough that does not add significant material, cost, or complexity to the tape head.